||Basic characteristics of alumina-based ceramics TLD to charged particle beams
古場, 裕介 ,
Chang, Weishan ,
Shinsho, Kiyomitsu ,
Yanagisawa, Shin ,
Sasaki, DaichWakabayashi, Genichiro
1. Introduction Charged particle therapy, such as proton and carbon therapy, became popular internationally as a radiation modality for cancer treatment. The verifications of the irradiation field or dose distribution in the charged particle therapy require the measurements with high spatial resolution, because these distributions are precipitous and complex. Recently, it was reported that the commercial Al2O3 ceramics plate showed good TL characteristics and available as 2D dosimeter . This ceramic TLD was very easy to deal and low-cost device, and with high spatial resolution. In order to use this ceramic TLD in the charged particle therapy as the verification tools, we investigated the thermoluminescence characteristics of the ceramic TLD to charged particle beams.2. Materials and MethodsIn this study, the ceramics TLDs (Chibacera cop. A8; Al2O3 : >99.5 wt%, SiO2 : <0.10 wt%, Fe2O3: <0.05 wt%, Na2O: <0.10 wt%) were used. Experiments of several charged-particle-beam irradiations were performed at the Heavy-Ion Medical Accelerator in Chiba (HIMAC) in the National Institute of Radiological Sciences. The beams of proton 160 MeV, He 150 MeV/u, C 290 MeV/u, Ne 400 MeV/u and Ar 500 MeV/u were used. And the X-ray irradiation was carried out using a Varian CLINAC-21EX Linear accelerator at 6 MV. In irradiations, four dose levels were given as 0.5, 1.0, 2.0 and 5.0 Gy in water concerning the predicted dose to the charged particle therapy. The glow curve of the ceramic TLD was measured using a photon counting unit (HAMAMATSU H11890-110) and a brass plate heater connected programmable heat controller (Sakaguchi E.H VOC CORP. SCR-SHQ-A). The glow curves were recorded from room temperature up to 400°C at a heating rate of 0.13°C/s in air. Thermoluminescence intensity was calibrated using 60Co gamma rays.3. Results & Discussion Figure 1 shows the glow curve of this alumina based ceramics TLD. The glow peaks were located at 148 °C (main peak) and 285 °C. Thermoluminescence intensity was evaluated using the range of 10 °C centered on the main peak. In any particle irradiation, dose linearity and repeatability was good comparatively. The standard deviation of variation coefficient of dose responses was less than 4% except for Ar irradiation. The TL efficiencies of each peak showed different LET dependence effect. Figure 2 shows the LET dependency of TL efficiency of main peak. The TL efficiency of the peak located at 148 °C showed small LET dependency as compared to common TLDs . In the range from 0.1 to 20 keV/m, LET dependency was less than 10%. In Ar irradiation, TL efficiency was about 80% at 86 keV/m. In dosimetry of charged particle therapy, solid state detectors such as TLD were avoided to use generally, due to such large LET dependency. This ceramics TLD might be available as a verification tool in limited LET range like as proton therapy.4. ConclusionsIn this study, basic characteristics of alumina-based ceramics TLD to charged particle beams were reported. The glow curve had two peaks, and main peak located at 148 °C showed good linearity and repeatability. The TL efficiency of the main peak showed small LET dependency as compared to common TLDs. This ceramics TLD might be available as a verification tool in limited LET range like as proton therapy.5. References K. Shinsho et al. X-ray imaging using thermoluminescence properties of commercialAl2O3 ceramics plates, Applied Radiation and Isotopes, in press. T. Bergera, M. Hajek, TL-efficiency—Overview and experimental results over the years, Radiation Measurements 43 (2008) 146-156.
The 18th International Conference on Solid State Dosimetry